Is there something wrong with our new combi gas boiler and plumbing?

Alex1983

Plumber wanted loft because it's a easy install.

Pre heat in my experience is useless. The boiler still has to fire and reach temperature and can never catch the pre heated water so you wait a while it gets hot you think it will stay hot but it won't because in only pre heats what inside the boiler and you still have to wait for the rest of the hot water.

Norman_Castle

Can the pressure or flow rate be reduced before or after the boiler to save the op adjusting it via the taps?

fezster

OP - get your gas safe engineer back asap and ask him to fix the issues you are having. There is no way you should accept a new combi boiler install with hot water taking over 2 minutes to reach your kitchen tap. For starters, it does not meet recommended guidelines of maximum one minute to any hot outlet to prevent legionellas:

http://www.hse.gov.uk/legionnaires/things-to-consider.htm


The engineer should have considered the pipe runs to the hot outlets and measured the incoming flow and pressure and chosen a boiler appropriately, or fitted a flow regulator to manage the flow, rather than you have to adjust the tap manually to make the boiler work. Hopefully you haven't paid him in full yet.

daveyjp

As it looks like a bit of a 'get it done quick' job one other thing to check. Where does the condensate pipe run to? It should be a white pipe exiting the property and plumbed into an open ended drain, not a downpipe which disappears into the ground, such as toilet soil stack.

Also check the pipe is well insulated if it has been run along an external wall. If not it could freeze in winter causing the boiler to trip out. Defrosting it will be a nightmare at high level.

Alex1983

Condense pipework doesn't have to go into a open ended drain. The most common termination is a 4" strap on boss into a 4" soil pipe. It shouldn't go into a rain water soak away unless it runs to a foul drain.

The easiest solution is to restrict the cold main to around the correct flow rate at the boiler.

A combination boiler stores less then 15 litres of water and is in regular use so is considering very low risk for legionaries.

fezster

Alex1983 wrote: »

A combination boiler stores less then 15 litres of water and is in regular use so is considering very low risk for legionaries.

It's the outlet which is at risk of legionnaires. Especially taps, because they will be run for short periods of time, and taking up to 2 minutes to reach their maximum temp means they will seldom do so.

Alex1983

I see your point and I know what the recommendations are but can't see it causing a problem in the real world and never have in 16yrs in the trade, if the cold inlet is only 5C-10C in mid winter and the boiler can only provide a 35C rise then the outlets will never get above the recommended 50C and certainly not within 1 minute.

Once the flow issue is sorted I don't think it will take anywhere near 2.5mins to get hot anyway.

daveyjp

Alex1983 wrote: »

Condense pipework doesn't have to go into a open ended drain. The most common termination is a 4" strap on boss into a 4" soil pipe. It shouldn't go into a rain water soak away unless it runs to a foul drain.

The easiest solution is to restrict the cold main to around the correct flow rate at the boiler.

A combination boiler stores less then 15 litres of water and is in regular use so is considering very low risk for legionaries.

It doesn't have to, but it saves a lot of grief if the soil pipe ever backs up.

southcoastrgi

Norman_Castle wrote: »

Can the pressure or flow rate be reduced before or after the boiler to save the op adjusting it via the taps?

That's what the handles or lever is for on the taps, if you want a slower flow rate don't open them up too much

C_Mababejive

I think the first step is to get someone competent to measure the current performance of the boiler. For this a flow measuring device and a thermometer are needed. Check that the temperature rise agrees with that stated in the spec for the given flow rate. If the flow rate is too high then it can be adjusted to match the spec. The Engineer would also have to check the gas pressure and gas rate to ensure correct heat input.

If all that matches up ok,,well its just tough. Maybe people buy combis but they dont always meet their aspirations or needs.

Someone has already mentioned temperature rise and the effect of weather on final water temp. Here i have a bog standard wall boiler fully pumpd heating a cylinder. The boiler is range rated down to about 9Kw.
It can produce a final tap outlet temp of 50c on its lowest setting.

Even better i have decent flow and it gets to the tap quickly,,no real wait.

Compare that with your Greenstar with a max output of 30Kw compared to my 9 Kw and yet i get better hot water performance. Why? Because i have storage.